Many thanks, mkk and kuzzia, for your kind replies.
1) i5 vs. i7.
The i5 3570K had been my first choice. I was seduced by an enthusiast's fascination with speed and technology to consider the i7 3770, but, you are right, it makes as much sense in this build as it does to take a bath in a swimming pool.
"K" unlocked CPUs in an H77 motherboard (see http://communities.intel.com/thread/29119
) seem problematic.
But perhaps the Z77 chipset would be a better choice, anyway. Underclocking instead of "S" or "T" versions for energy efficiency?
2) Lian-Li power switch.
I am already using the Lian-Li power switch in another build (Intel DH67BL, one SSD, three HDDs, two separately booted operating systems) and have been very pleased. Of course, the respective OS must be separately booted (all drives turned off except for the booting drive), but I have no problems mounting non-OS drives under Windows, turning them off and on (and the S-ATA optical drive as well) while the computer is running. This nicely partitions off Internet from work applications and ensures overall quietness and economical energy usage.
Of course, ASUS has UEFI, a different BIOS, and I want to install two SSDs--and that may pose some challenges. Whether the SSDs would suffer--TRIM, for example--is a question I cannot answer and one I hope you could. Making BIOS changes, if required, might resolve issues.
3) HR-02 vs. Mugen.
Mugen is said to be a fine choice for a quiet PC and it was my first choice as well. But I wanted to try out Noiseblocker fans throughout the build to improve the overall sound signature and the HR-02 design appealed to me.
Without a discrete GPU, I think you're right, I could get away with a HS fan and exhaust fan, especially if the four HDDs/SSDs are not switched on at the same time.
By the way, in another build, I had a bottom intake fan (Papst) and a Noctua HS and fan. I removed the exhaust fan experimentally and its removal had little or no effect on operating temps. Wonders of positive pressure. That was a minimalist office build, though.
4) 16 GB vs. 12 GB.
Many would say that 8 GB would be perfectly sufficient. However, RAM is relatively cheap and occasionally I work with several programs simultaneously, including Dragon Naturally Speaking, a notorious memory hog. So, it was a question of 12 or 16 GB and I decided to go with 12 GB because according to one study I read, 16 GB doesn't add that much more than 12 unless you are doing video rendering, etc.
5) I like Fractal but I also admire the Antec performance line and would like to try out one of their quality cases.
The Seasonic X series fanless are interesting but you have to have adequate ventilation elsewhere, so in the end you may have to add extra fans, thus defeating the purpose. Note, too, that a PSU fan is also drawing air out of the case.
Honestly, I am not even sure what the best PSU would be in a rig like this one. Should I use higher wattage to ensure lower temps? And it is a guessing game with PSUs, especially since so much depends on the mainboard. My main candidates are Enermax, BeQuiet, and the above CoolerMaster.